The military environment is changing, e.g., the operating environment is becoming more varied and demanding. Due to these challenges, new user interfaces (UIs) are required providing improved soldier protection and performance both in day-time and night-time conditions. The new UIs should, e.g., improve the soldier's situation awareness, i.e., perception of information, integration of pieces of information, determination of their relevance to one's goals, and projection of their status in the future. The aim of the Finnish project called "Supporting situation awareness in demanding operating environments through wearable interfaces" is to develop UIs for wearable computers that help the special force soldier carry out his/her main critical tasks, e.g., detection and identification of enemies and features of the surrounding environment, navigation and self-localization, development of tactics and communication between and within military units. The main portions of t...